(a) Technical Field
Embodiments of the present invention relate generally to touch-sensitive display devices. More specifically, embodiments of the present invention relate to in-cell touch type display devices.
(b) Description of the Related Art
Display device technology has seen rapid recent changes. More particularly, a flat panel display having lower profile, light weight, and low power consumption has recently been replacing the conventional cathode ray tube (CRT).
Since one type of flat panel display, the organic light emitting diode display device, is non-emissive, its viewing angle, contrast, etc., are relatively high, and since a backlight is not needed as compared with a liquid crystal display, the organic light emitting diode display device can be thin and lightweight and is advantageous in terms of power consumption. Also, since the organic light emitting diode display device may be driven with a low DC voltage, has a rapid response speed, and is solid, the organic light emitting diode display device tends to be relatively resistant to external impact, has a wide usage temperature range, and particularly, has a low manufacturing cost.
On the other hand, a touch type display device that is capable of inputting a user command by selecting a screen of the image display device by e.g. a hand or another object, is widely used.
To achieve this, the touchscreen panel is disposed on a front face of the image display device to convert a contact position where the person's hand or the object touches, into an electric signal. Accordingly, the instruction selected in the contact position is input as an input signal.
The touch sensing function may be implemented by a touch sensor. The touch sensor may be classified into various touch sensing types such as a resistive type, a capacitive type, an electromagnetic resonance (EMR) type, and an optical sensing type.
In the case of a resistive type touch sensor, two electrodes spaced apart from each other while facing each other may contact each other by a pressure from an external object. When the two electrodes contact each other, the contact positions and the like may be determined by recognizing a change in voltage depending on a change in resistance at the contact position.
The capacitive type touch sensor includes a detection capacitor formed of a detection electrode capable of transferring a detection signal and detecting a change in capacitance of the detection capacitor that is generated when conductors, such as a finger, approach the sensor. This change in capacitance allows the sensor to determine whether contact has occurred, the contact positions, and the like.
The contact detecting sensor may be formed in the touch panel to be attached to the display device (an add-on cell type), may be formed outside a substrate of the display device (an on-cell type), and may be formed inside the display device (an in-cell type). The display device including the contact sensing sensor detects whether the finger of the user or the touch pen contacts the screen, as well as the contact position thereof.
These various touch sensors are disposed in the touch region, and include a plurality of touch electrodes to sense the touch, as well as connection wires connected to the touch electrode. The touch region may overlap the display area. The connection wires may transmit a sensing input signal to the touch electrode. They may also transmit a sensing output signal from the touch electrode generated according to the touch, to a sensing signal controller.
The add-on cell type of liquid crystal display may exhibit certain drawbacks. For example, the thickness of the display device is increased by the touch channel, and the manufacturing cost is increased by a touch panel formation process and a separate substrate required for the touch panel.
Further, the in-cell type display device forming a contact sensing sensor inside the display device limits the structure of the display device when applying it. For example, in the case of the display device in which the electrode is formed in the display panel including the thin film transistor, to prevent static electricity of the upper panel, a rear surface transparent electrode layer is formed in the upper panel. However the rear surface transparent electrode layer often inhibits touch recognition.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.